Phase structure of spin-imbalanced unitary Fermi gases

TL;DR

This paper uses the Functional Renormalization Group to analyze the phase diagram of spin-imbalanced unitary Fermi gases, revealing detailed phase transitions and potential experimental signatures beyond mean-field predictions.

Contribution

It introduces a systematic FRG approach to accurately map the phase diagram, including first- and second-order transitions, and discusses experimental implications.

Findings

Full phase diagram in temperature and spin-imbalance plane

Identification of first- and second-order phase transitions

Potential experimental signatures in density images

Abstract

We investigate the phase structure of spin-imbalanced unitary Fermi gases beyond mean-field theory by means of the Functional Renormalization Group. In this approach, quantum and thermal fluctuations are resolved in a systematic manner. The discretization of the effective potential on a grid allows us to accurately account for both first- and second-order phase transitions that are present on the mean-field level. We compute the full phase diagram in the plane of temperature and spin-imbalance and discuss the existence of other conjectured phases such as the Sarma phase and a precondensation region. In addition, we explain on a qualitative level how we expect that in-situ density images are affected by our findings and which experimental signatures may potentially be used to probe the phase structure.